1. Field of the Invention
The present invention relates to an integrated circuit package.
2. Background Information
Integrated circuits are typically assembled into a package that is soldered to a printed circuit board. There are various types of integrated circuit packages including ball grid array (BGA) packages. BGA packages include a plurality of solder balls that are attached to corresponding contact pads of a package substrate. The solder balls are reflowed to create solder joints which attach the package to the printed circuit board. The contact pads are typically circular in shape and arranged in a two dimensional array across the bottom surface of the package. An integrated circuit is mounted to the package substrate and coupled to solder balls by vias and routing traces of the substrate.
The package and circuit board are typically attached to an assembly which is exposed to an environment which may undergo variations in temperature. The changes in temperature will cause the circuit board and package to expand and contract. The thermal coefficient of expansion of the circuit board is different than the thermal expansion coefficient of the package. The difference in the thermal coefficients create stresses in the solder joints when the assembly is thermally cycled. It has been found that the stresses will induce cracks which propagate across the solder joints. The cracks may create electrical opens that render the package inoperable. It would be desirable to provide an integrated circuit package which increases the life of the solder joints over packages found in the prior art.